BLToolkit select unnecessary field.

see here http://www.rsdn.ru/forum/prj.rfd/5027715.1

				var q =
					from person in db.Person
					join patient in db.Patient on person.ID equals patient.PersonID into g
					from patient in g.DefaultIfEmpty()
					orderby person.MiddleName // if comment this line then "Diagnosis" is not selected.
					select new { person.ID, PatientID = patient != null ? (int?)patient.PersonID : null };
				// ReSharper disable ReturnValueOfPureMethodIsNotUsed
				q.ToList();
				// ReSharper restore ReturnValueOfPureMethodIsNotUsed

				Assert.IsFalse(db.LastQuery.Contains("Diagnosis"), "Why do we select Patient.Diagnosis??");